X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao106.cox.net ([68.230.241.40] verified) by logan.com (CommuniGate Pro SMTP 5.3.8) with ESMTP id 4411483 for flyrotary@lancaironline.net; Thu, 29 Jul 2010 17:31:27 -0400 Received-SPF: softfail receiver=logan.com; client-ip=68.230.241.40; envelope-from=glasair2@me.com Received: from fed1rmimpo02.cox.net ([70.169.32.72]) by fed1rmmtao106.cox.net (InterMail vM.8.00.01.00 201-2244-105-20090324) with ESMTP id <20100729213053.KYID1296.fed1rmmtao106.cox.net@fed1rmimpo02.cox.net> for ; Thu, 29 Jul 2010 17:30:53 -0400 Received: from [192.168.2.201] ([70.177.24.126]) by fed1rmimpo02.cox.net with bizsmtp id nxWp1e0082jEC4N04xWsGU; Thu, 29 Jul 2010 17:30:52 -0400 X-VR-Score: -100.00 X-Authority-Analysis: v=1.1 cv=8ImjV4Az/FeJ/TCHtNMSSkPeMQ/82ycixFxo4weeFA8= c=1 sm=1 a=7mRKtoZ49N4A:10 a=f32ykCDtWUuHg+z19x9HKQ==:17 a=oBdLjE-hAAAA:8 a=3oc9M9_CAAAA:8 a=HHGDD-5mAAAA:8 a=Ia-xEzejAAAA:8 a=7g1VtSJxAAAA:8 a=9i30IddzgTrktA9tbuYA:9 a=LroKFTpKmxhWQ0OUwVIA:7 a=F7br7NDMi12DKJAWvzjelDzM1vwA:4 a=wPNLvfGTeEIA:10 a=Qa1je4BO31QA:10 a=184Z8XVtRNwA:10 a=U8Ie8EnqySEA:10 a=i1zE5R4R5dEA:10 a=EzXvWhQp4_cA:10 a=LkQY913XJ9tHCw_GkxwA:9 a=LM9C-N5qGcZhlUPxKkAA:7 a=2gm5eIS3z3IUCK3vv0UV1cTxd9MA:4 a=f32ykCDtWUuHg+z19x9HKQ==:117 X-CM-Score: 0.00 From: Steve Thomas Mime-Version: 1.0 (Apple Message framework v1081) Content-Type: multipart/alternative; boundary=Apple-Mail-10--663345219 Subject: Re: [FlyRotary] Re: Noise Measurements Date: Thu, 29 Jul 2010 14:30:49 -0700 In-Reply-To: To: Rotary motors in aircraft References: Message-Id: <5D4D4FF5-D959-470E-B6D4-2FC6F502B108@me.com> X-Mailer: Apple Mail (2.1081) --Apple-Mail-10--663345219 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=iso-8859-1 Well, I just made a guess and measured it at 100 ft. I'll measure = cockpit noise later, when I've got some flight time in. Here is my = story: I have a Glasair Super II RG with a Mistral 2 rotor engine. I've had it = in the air once, and landed immediately as there was an oil temp problem = that turned out to be a measurement problem. However, what I did find = that was particularly annoying was the noise. My LightSpeed Zulu = handled the noise fine until I keyed the mic. Man, what a blast of = noise! I could barely hear the tower. =20 The muffler that I was using was a 2 1/2 inlet/outlet and 3 1/2" = diameter Burns Stainless device that I purchased many moons ago. It was = made up with stainless scrubble innards. So, I decided to replace it = with another Burns Stainless muffler, but a 2 1/2" inlet/outlet, 6 1/4" = diameter, dual stage muffler. See: =20 http://www.burnsstainless.com/sm-300-625-17-2s.aspx Although this one has a 3" inlet/outlet, they made one for me with the 2 = 1/2". What a difference!!!! Here are the measurements I took from 100 = feet, off the wing tip and about 30=BA aft. They also put in a = stainless cloth material instead of the stainless scrubble. They claim = that it works great for the rotary. =20 idle: 57-60 DB 1500 RPM: 78 DB 2000 RPM: 87DB By RPM, I mean prop at 2.85-1 reduction ratio. I was fearful that going = any higher would put my prop too close to the ground as the nose gear = compressed down with power. I suppose you math-types can extrapolate = different distances. =20 I'll be hitting the air tomorrow. While I had one short flight already, = this will be much longer, hopefully and I can see what the plane will = do. The only real disadvantage of the muffler is that it hangs underneath = the belly and looks ugly. But it, so far, works terrific. I hope the = drag penalty is not too great. =20 BTW, the rest of my exhaust consists of 2" headers into a collector with = a 2 1/2" outlet made with .065 321 SS. =20 Best Regards, Steve Thomas _______________________________________________________ On Jul 29, 2010, at 12:52 PM, wrjjrs@aol.com wrote: > Steve, > =20 > Typically the measurement for cars and motorcycles is at 50 feet away = at 90 degrees to the directin of the exhaust flow. Any in-cabin = measurements wouldn't need orientation, just put the pick up about where = your head is. > =20 > Bill Jepson >=20 >=20 >=20 > -----Original Message----- > From: Steve Thomas > To: Rotary motors in aircraft > Sent: Thu, Jul 29, 2010 9:31 am > Subject: [FlyRotary] Noise Measurements >=20 > I want to take some noise measurements today with a new muffler I just=20= > installed. What is a reasonable distance from the aircraft to be = taking these=20 > measurements? Right next to the airplane seems to be somewhat = unreasonable, and=20 > distance makes a big difference. =20 >=20 > Best Regards, >=20 > Steve Thomas > _______________________________________________________ >=20 >=20 >=20 >=20 >=20 >=20 > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html --Apple-Mail-10--663345219 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=iso-8859-1 Well, = I just made a guess and measured it at 100 ft.  I'll measure = cockpit noise later, when I've got some flight time in.  Here is my = story:

I have a Glasair Super II RG with a Mistral 2 = rotor engine.  I've had it in the air once, and landed immediately = as there was an oil temp problem that turned out to be a measurement = problem.  However, what I did find that was particularly annoying = was the noise.  My LightSpeed Zulu handled the noise fine until I = keyed the mic.  Man, what a blast of noise!  I could barely = hear the tower.  

The muffler that I was = using was a 2 1/2 inlet/outlet and 3 1/2" diameter Burns Stainless = device that I purchased many moons ago.  It was made up with = stainless scrubble innards.  So, I decided to replace it with = another Burns Stainless muffler, but a 2 1/2" inlet/outlet, 6 1/4" = diameter, dual stage muffler.   See: =  


Althou= gh this one has a 3" inlet/outlet, they made one for me with the 2 1/2". =  What a difference!!!!  Here are the measurements I took from = 100 feet, off the wing tip and about 30=BA aft.  They also put in a = stainless cloth material instead of the stainless scrubble.  They = claim that it works great for the rotary. =   

idle:  57-60 = DB
1500 RPM:  78 DB
2000 RPM: =  87DB

By RPM, I mean prop at 2.85-1 = reduction ratio.  I was fearful that going any higher would put my = prop too close to the ground as the nose gear compressed down  with = power.  I suppose you math-types can extrapolate different = distances.  

I'll be hitting the air = tomorrow.  While I had one short flight already, this will be much = longer, hopefully and I can see what the plane will = do.

The only real disadvantage of the muffler = is that it hangs underneath the belly and looks ugly.  But it, so = far, works terrific.  I hope the drag penalty is not too great. =  

BTW, the rest of my exhaust consists of = 2" headers into a collector with a 2 1/2" outlet made with .065 321 SS. =  

Best Regards,

Steve = Thomas




=

On Jul 29, 2010, at 12:52 PM, wrjjrs@aol.com wrote:

Steve,
 
Typically the measurement for cars and motorcycles is at 50 feet = away at 90 degrees to the directin of the exhaust flow. Any in-cabin = measurements wouldn't need orientation, just put the pick up about where = your head is.
 
Bill Jepson

= --Apple-Mail-10--663345219--